Magnets have been around for centuries, but the history of their manufacture is a more recent development. The first magnet to be mass-produced was the Alnico Magnet in the 1930s. The Ferrite Magnets in the 1950s, Samarium Cobalt Magnets in the 1960s, and Neodymium Magnets in the 1980s. While these magnets are now widely used for a variety of applications, it is important that it all started with Lodestone – An naturally occurring form of magnetite – which was used as early as 600 BC.
Compare 4 types of permanent magnets: Alnico Ferrite SmCo NdFeB
- Alnico magnet (1930’s)
- Ferrite Magnet (1950’s)
- Samarium Cobalt Magnet (1960’s)
- Neodymium Magnet (1980’s)
1). Neodymium Iron Boron Magnet
Neodymium Iron Boron is the strongest type of permanent magnet available commercially. It is a permanent magnet made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. It is the most widely used type of rare-earth magnet.
Neodymium magnet (also known as NdFeB, NIB or Neo magnet) was discovered in 1982 by Masato Sagawa from Sumitomo Special Metals.
The Sumitomo facility became part of the Hitachi Corporation, and has developed powder metallurgy process to manufacture but they also licensed other companies to produce sintered Nd2Fe14B magnets.
General Motors (GM) focused on the development of melt-spun nanocrystalline Nd2Fe14B magnets, GM commercialized its inventions of isotropic Neo powder, bonded neo magnets, and the related production processes by founding Magnequench in 1986.
Chinese manufacturers have become a dominant force in neodymium magnet production, based on the abundant resource of rare-earth mines.
2). Samarium Cobalt Magnet
Samarium–Cobalt (SmCo) magnet, a type of rare-earth magnet, is a strong permanent magnet made of two basic elements: samarium and cobalt.
They were developed in the early 1960s based on work done by Karl Strnat at Wright-Patterson Air Force Base and Alden Ray at the University of Dayton. In particular, Strnat and Ray developed the first formulation of SmCo5.
Samarium–cobalt magnets are generally ranked similarly in strength to neodymium magnets, but have higher temperature ratings and higher coercivity. The cost of SmCo magnet is expensive, the research of NdFeB was initially driven by the high raw materials cost of SmCo permanent magnets.
3). Ferrite Magnet
A Ferrite Magnet is a ceramic material made by mixing and firing large proportions of iron(III) oxide (Fe2O3, rust) blended with small proportions of one or more additional metallic elements, such as strontium, barium, manganese, nickel, and zinc. Ferrite magnet are extremely low cost, being made of mostly iron oxide, and have excellent corrosion resistance.
Yogoro Kato and Takeshi Takei of the Tokyo Institute of Technology synthesized the first ferrite compounds in 1930. This led to the founding of TDK Corporation in 1935, to manufacture the material.
Barium hexaferrite (BaO•6Fe2O3) was discovered in 1950 at the Philips Natuurkundig Laboratorium (Philips Physics Laboratory). Barium hexaferrite has both high coercivity (170 kA/m) and low raw material costs. It was developed as a product by Philips Industries (Netherlands) and from 1952 was marketed under the trade name Ferroxdure. The low price and good performance led to a rapid increase in the use of permanent magnets.
In the 1960s Philips developed strontium hexaferrite (SrO•6Fe2O3), with better properties than barium hexaferrite. Barium and strontium hexaferrite dominate the market due to their low costs. Other materials have been found with improved properties. BaO•2(FeO)•8(Fe2O3) came in 1980.[26] and Ba2ZnFe18O23 came in 1991.
4). AlNiCo Magnet
Alnico is a family of iron alloys which in addition to iron are composed primarily of aluminium (Al), nickel (Ni), and cobalt (Co), hence the acronym al-ni-co. They also include copper, and sometimes titanium. The composition of alnico alloys is typically 8–12% Al, 15–26% Ni, 5–24% Co, up to 6% Cu, up to 1% Ti, and the rest is Fe. Alnico alloys are ferromagnetic, and are used to make permanent magnets.
Alnico was the earliest developed permanent magnet, the development of alnico began in 1931, when T. Mishima in Japan discovered that an alloy of iron, nickel, and aluminium had a coercivity of 400 oersteds (32 kA/m), double that of the best magnet steels of the time. Before the development of rare-earth magnets in the 1970s, they were the strongest type of permanent magnet.
5). Lodestone
Lodestone is natural magnet and not manufactured by human, but it is been known and used by people for thousands of years. Lodestones are naturally magnetized pieces of the mineral magnetite. They are naturally occurring magnets, which can attract iron.
One of the earliest known references to lodestone’s magnetic properties was made by 6th century BC Greek philosopher Thales of Miletus, whom the ancient Greeks credited with discovering lodestone’s attraction to iron and other lodestones. The name magnet may come from lodestones found in Magnesia, Anatolia.
